2002 S60 Rough idle but smooth at higher RPM

quietcoolone · Post by **quietcoolone** » 02 Jan 2015, 20:06

Please help. I just picked up a 2002 S60 (not turbo) with 300K+ mile for my daughter commute to school and they are a few things that need help with the following.
The car runs (starts every time i turn the key) but has a rough idle. If i rev it up to say 2500RPM and let go of the throttle, the engine idle is normal or until i put in gear at which point it reverts to bad idle
I have performed the following:
1. Cleaned the MAF
2. Cleaned the Throttle Body (Vida ETM test resulted in max angle difference of 2.9 degrees)
3. Cleaned the PCV system
4. Replaced spark plugs
5. Reset the computer so it can re-learn the new trims.
I've connected my scan tool to monitor fuel trims:
At idle STFT is 25.0 LTFT 0.0
at 2500RPM STFT is -1.6 LTFT 0.0.
release throttle STTT -1.6 LTFT 0.0..
car in gear (idling) STFT goes up to 18.0 and LTFT 14.9

This cycle repeats after each start...
To summarize:
The car starts and revs up to about 1500 RPM then come down to about 800, then it will begin to shake as if it is stalling, if I press on the accelerator the car runs fine or until it put in gear then it will shake and want to stall.
Note that disconnecting the MAF makes the car idle smooth.
Any help is appreciated.

2008XC70 · Post by **2008XC70** » 03 Jan 2015, 01:24

If it runs better with MAF disconnected, that could be suspect. How are the ignition coils? Any hairline cracks in them?

quietcoolone · Post by **quietcoolone** » 03 Jan 2015, 03:12

2008XC70 wrote:If it runs better with MAF disconnected, that could be suspect. How are the ignition coils? Any hairline cracks in them?

I failed to mention that in addition to cleaning the MAF (CRC 05110), i also tried another (part #9202199) from a loaner car with same results (i also tried another from a pick-your-own parts car depot)
Ignition coils are firing and boots are in good condition.
(I have gotten a P0300 (misfire all cylinders), but that is unlikely because of ignition coils or plugs.).
Vida MAF show (in Park):
Voltage (idle): 1.24 @ 3.02 g/s
Voltage (2500 RPM): 1.78 @ 8.8 g/s
Once in gear it begins to run rough and misfire (MAF 1.20V and 2.6 g/s)
any other test i can run on Vida or live data information needed to troubleshoot, let me know and i will gladly provide it.

Thank you.

draser · Post by **draser** » 03 Jan 2015, 08:55

Your STFT highly positive at idle only points to an air leak. MAF seems to work okay based on the same observation of the fuel trims.

quietcoolone · Post by **quietcoolone** » 03 Jan 2015, 09:06

draser wrote:Your STFT highly positive at idle only points to an air leak. MAF seems to work okay based on the same observation of the fuel trims.

draser, i tend to agree but finding that sucker it going to be difficult. I have sprayed carburetor cleaner around intake manifold, brake booster hose, MAP hose and small intake hose to Air Filter box with no change in engines RPM. any ideas where else to check for possible air leak?

Post by **oragex** » 03 Jan 2015, 13:56

Failed ETM? Burnt valve? Leaking head gasket? Part clogged injector?

draser · Post by **draser** » 03 Jan 2015, 14:18

Can you see fuel pressure with your scanner?

draser · Post by **draser** » 04 Jan 2015, 08:43

Thinking out loud.. your MAF idle level is higher than my number but I have a turbo.. Not sure what it should be for NA. Hopefully someone chimes in. When you replaced those MAFs you used correct p/ns of course?

quietcoolone · Post by **quietcoolone** » 04 Jan 2015, 20:31

well, the part number on the original MAF is 9202199, which matches that of the others i've tested.
Could not find a fuel pressure parameter in Vida but found a pressure gauge and its 55 psi (Engine running)
So, STFT is very high (+25) at startup (idle), car runs rough,Vida cylinder misfire count upwards on all cylinders.
At 2500RPM engine runs smooth, STFT moves slowly to between -2.3 and 0; release accelerator (back to idle) and car continues to run smooth, however if i put car in D or R , idles rough and SFTF goes back up.

Thanks

draser · Post by **draser** » 05 Jan 2015, 14:10

If the misfire condition is combined with fuel trim numbers it points to a headgasket, do you lose coolant?